Figure 4: The recovery effects of BK channel or PLA₂ inhibitors on the increased neurotransmission in lamina I neurons.

(a) Typical traces of mEPSCs recorded from the lamina I spinal neurons after 5 days of saline or morphine (10 mg kg⁻¹) treatment. BK channel (2.2 μg kg⁻¹, i.p.) or PLA₂ inhibitors (100 pmol, i.t.) were administered 30 min prior to morphine treatment. (b,c) The averaged frequency (b) and amplitude (c) of mEPSCs (n=8 from three mice for Saline, n=6 from three mice for Morphine, n=9 from three mice for Morphine+Paxilline, n=13 from four mice for Morphine+AACOCF₃). Sal, Pax and AACO indicate saline, paxilline and AACOCF₃, respectively. (d) Typical traces of dorsal root entry stimulated currents recorded from the lamina I spinal neurons after 5 days of morphine treatment. The triangles indicate dorsal root stimulation. A second stimulus was delivered 50 ms after the first. (e) The PPR was calculated as the ratio of the 2nd/1st responses. (f) The current–intensity curves of the dorsal root-evoked currents. The half values of I/I_MAX were 1.739 mA (Saline), 1.180 mA (Morphine), 1.652 mA (Morphine+Paxilline) and 1.571 mA (Morphine+AACOCF₃). (n=7 for Saline, n=8 for Morphine, n=9 for Morphine+Paxilline, n=7 for Morphine+AACOCF₃, from three mice each). The data represent the means±s.e.m. *P=0.0124 (Saline versus Morphine), **P=0.0062 (Morphine versus Morphine+Paxilline), **P=0.0091 (Morphine versus Morphine+AACOCF₃), F_{3, 31}=5.127, a one-way ANOVA followed by the Tukey’s post hoc test (b). *P=0.0112 (Saline versus Morphine), **P=0.0035 (Morphine versus Morphine+Paxilline), *P=0.00110 (Morphine versus Morphine+AACOCF₃), F_{3, 31}=0.2830, a one-way ANOVA followed by the Tukey’s post hoc test (e), *P=0.0445 (Saline versus Morphine), ^†P=0.0427 (Morphine versus Morphine+Paxilline) and ^#P=0.0404 (Morphine versus Morphine+AACOCF₃), (drug × time point interaction): F_{3, 162}=5.51, a two-way ANOVA followed by the Bonferroni post hoc test (f). Scale bars, 20 pA and 100 ms (a); and 50 pA and 10 ms (d).